Cocaine abuse in the United States is a major public health concern. Cocaine use leads to activation of specific circuits in the brain, most notably mesolimbic dopamine neurons. With continued use, neuroadaptive changes occur in these neurons which lead to even more protracted use of the drug. Significant progress has been made in the elucidation of the biochemical mechanisms underlying the neuroadaptive changes, however, the regulation of gene transcription by cocaine in human post-mortem tissue has received considerably less attention. The first aim will compare regional gene expression between the ventral tegmental area (VTA) versus lateral substantial nigra (l-SN) and nucleus accumbens (NAc) versus dorsal caudate-putamen (d-CP) in post-mortem tissue from cocaine overdose victims and age-matched, non-drug controls. Based on preliminary data, we predict chronic cocaine use is preferentially associated with altered expression of genes encoding dopamine- and signal transduction-related proteins in the VTA and NAc compared with the l-SN and d-CP, respectively. In the second aim, we will examine the gene expression in a discrete neuronal population by comparing profiles of tyrosine hydroxylase immuno-positive neurons in the VTA and 1-SN between cocaine overdose victims and controls. To this end, we predict preferentially altered expression of genes encoding dopamine- and signal transduction-related proteins in dopamine neurons in the VTA compared with the l-SN in cocaine overdose victims. This aim is based on the idea that coordinate dysregulation of several genes in discrete neuronal populations is linked to cocaine abuse. Results from these studies will provide correlative evidence of the involvement of multiple transcripts and a detailed expression profile of human cocaine abuse. The final aim is to evaluate changes in protein levels and function associated with the expression profile of genes, in particular dopamine related and signal transduction-related proteins. The application will utilize human post-mortem tissue and state-of-the-art regional and single neuron expression and cDNA array methodologies to provide the first extensive expression profile of cocaine addiction. Characterization of altered expression patterns for thousands of genes will provide a panoramic view of the potential molecular underpinnings of cocaine reinforcement and the neuroadaptive changes in these neurons associated with long-term use. In addition, identification of differentially expressed genes may provide novel targets for the pharmacotherapeutic development and/or the refinement of existent pharmacotherapies.